Hi Eric,
I probably did not perform a suitable warmup as I had considered that was more of a drift issue than anything. I presumed that if I can't get a +/- swing cold, then something may be wrong but that may not be correct. I'm letting it do a proper warmup and will recheck.
I'm pretty sure I was checking that via the output connector (per the manual) so that shouldn't have offset the oscillator with unnecessary capacitance (but thanks for the reminder about that).
Thanks,
Barry - N4BUQ
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----- Original Message -----
From: "Eric" <ericsp@...>
To: "tekscopes" <[email protected]>
Sent: Monday, December 6, 2021 11:55:53 PM
Subject: Re: [TekScopes] 10Mhz under frequency in 184 Time-Mark Generator
How long a warmup time are you giving the crystal before trying to cal.
Also how is your probing set up? This circuit is incredably sensitive to
capacitance. Not enough heat in the crystal and or too much capacitance in
the probing set up will drag the crystal off to the low side of things.
Eric
On Tue, Dec 7, 2021, 12:41 AM Jeff Dutky <jeff.dutky@...> wrote:
The advertised spec is +/- 0.001%, so (if my math is right) you are will
within the advertised precision.
The circuit in which Y11 operates looks pretty simple, the only components
around it are C11, R11, L18, and V10. I'd have a look at R11 to be sure it
hadn't drifted (the parts list seems to indicate that it's an unremarkable
carbon comp resistor, with 10% accuracy). You could also remove the
Nuvistor and the crystal in order to check C11 in place. I expect that both
V10 and Y11 are socketed, but I can't really tell about the crystal oven
from the pictures in the service manual, so it might be easier to unsolder
C11 than to remove Y11.
-- Jeff Dutky
